Charith's Blog

Tuesday, November 16, 2010

How to output web page as MS word document

public partial class Test : Page
{
    protected override void Render(HtmlTextWriter writer)
    {
        Response.Clear();
        Response.Buffer = true;
        Response.ContentType = "application/msword";
        StringBuilder sb = new StringBuilder();
        StringWriter stringWriter = new StringWriter(sb);
        HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter);
        base.Render(htmlTextWriter);
        Response.Write(sb.ToString());
        Response.End();            
    }
}

Friday, November 12, 2010

How to keep track of selected file during a postback.

When you select a file and then do a postback, you will lose your selected file. This is because there is no ViewState for posted file in asp.net FileUpload control. This example is to demonstrate an idea of how to save the file in any-postback and if there is a selected file, then we save the file and show the fileName in a hyperlink to download or view,
Example:

<%@ Page Language="C#" %>
<html>
<head id="Head1" runat="server">
    <script runat="server">
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            if (this.fuFile.HasFile)
            {                
                string filePath = Server.MapPath(string.Format("~/Uploads/{0}", this.fuFile.FileName));
                if (!System.IO.File.Exists(filePath))
                {
                    this.fuFile.SaveAs(filePath);
                    this.linkSelectedFile.NavigateUrl

                        = this.ResolveUrl(string.Format("~/Uploads/{0}", this.fuFile.FileName));

                    this.linkSelectedFile.Text = this.fuFile.FileName;
                }
            }
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        Select a File: <asp:FileUpload runat="server" ID="fuFile" />
        <asp:HyperLink runat="server" ID="linkSelectedFile" />
        <hr />
        <asp:DropDownList runat="server" ID="ddlItems" AutoPostBack="true">
            <asp:ListItem>Item One</asp:ListItem>
            <asp:ListItem>Item Two</asp:ListItem>
        </asp:DropDownList>
    </form>
</body>
</html>

Tuesday, November 02, 2010

How to disable past days in asp.net calender control

<%@ Page Language="C#" %>
<html>   
<head id="Head1" runat="server">  
    <script runat="server">
        protected void DisablePastDays(object sender, DayRenderEventArgs e)
        {
            if (e.Day.Date < DateTime.Now)
            {
                e.Cell.Enabled = false;
                e.Day.IsSelectable = false;
                e.Cell.BackColor = System.Drawing.Color.Gray;
            }
        } 
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <asp:Calendar runat="server" ID="calDate" OnDayRender="DisablePastDays" />
    </form>
</body>
</html>

How to add detail textbox opon the check of a check box

Demo:
Example:
Markup:

<%@ Page Language="C#" %>
<html>   
<head id="Head1" runat="server">  
</head>
<body>
    <form id="form1" runat="server">
        <asp:FreeCheckBox runat="server" 
            ID="freeCheckBox" 
            DetailPlaceHolderId="phDetails" 
            Text="Are you disabled?" 
            DetailLabel="Please please provide details" />
        <asp:PlaceHolder runat="server" ID="phDetails" />
        <hr />
        <asp:Button runat="server" ID="btnSave" Text="Save" />
    </form>
</body>
</html>

Control:

public class FreeCheckBox : CheckBox
{
    private TextBox txtDetail;
    private Panel pnlDetail;
    private string script = @"
    function ShowHideDetailPanel(detailPanel, source) {            
        var panel = document.getElementById(detailPanel);
        if (panel == undefined) return;
        if (source.checked == true)
            panel.style.display = ""block"";
        else
            panel.style.display = ""none"";
    }
";
    public string DetailLabel { get; set; }
    public string Details { get; set; }
    public string DetailPlaceHolderId { get; set; }
    public bool IsMultiline { get; set; }
    public FreeCheckBox()
    {
        this.DetailPlaceHolderId = string.Empty;
        this.IsMultiline = false;
    }
    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);
        this.CreateControlHeirarchy();
    }
    public void CreateControlHeirarchy()
    {
        this.pnlDetail = new Panel() { ID = string.Concat(this.ID, "_DetailPanel"), CssClass = "DetailPanel" };
        this.txtDetail = new TextBox() { ID = string.Concat(this.ID, "_TextBox"), 
                                            CssClass = "DetailTextBox", TextMode = TextBoxMode.MultiLine };
        if (this.IsMultiline) this.txtDetail.TextMode = TextBoxMode.MultiLine;
        this.pnlDetail.Controls.Add(new Label() { Text = this.DetailLabel, CssClass = "DetailLabel" });
        this.pnlDetail.Controls.Add(this.txtDetail);
        PlaceHolder phDetail = this.Page.FindControl(this.DetailPlaceHolderId) as PlaceHolder;
        Control parent = this.Parent;
        while (phDetail == null)
        {
            phDetail = parent.FindControl(this.DetailPlaceHolderId) as PlaceHolder;
            if (phDetail == null) parent = parent.Parent;
            if (parent == null) break;
        }
        if (phDetail != null) phDetail.Controls.Add(pnlDetail);
        this.Attributes.Add("onclick", 
                string.Format("javascript:ShowHideDetailPanel('{0}', this)", pnlDetail.ClientID));
    }
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        if (this.Checked)
            this.pnlDetail.Attributes.Add("style", "display:block;");
        else
            this.pnlDetail.Attributes.Add("style", "display:none;");
    }
    protected override bool LoadPostData(string postDataKey, NameValueCollection postCollection)
    {
        bool value = base.LoadPostData(postDataKey, postCollection);
        if (this.Checked)
            this.Details = this.txtDetail.Text;
        return value;
    }
    protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);
        this.Page.ClientScript.RegisterClientScriptBlock(
                this.GetType(), this.GetType().Name, this.script, true);
    }
}

How to download images

Demo:
Code:

<%@ Page Language="C#" %>
<html>   
<head id="Head1" runat="server">  
    <script runat="server">
        public void DownloadPicture(object sender, EventArgs e)
        {
            ImageButton button = sender as ImageButton;
            if (button != null)
            {
                string fileName = button.CommandArgument;
                this.Response.AddHeader("content-disposition", 
                    string.Format("attachment;filename={0}", Path.GetFileName(fileName)));
                this.Response.ContentType = "image/jpg";
                this.Response.WriteFile(this.Server.MapPath("~/Images/" + fileName));
            }
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <asp:ImageButton runat="server" ID="btnPic1" Text="Pic 1" CommandArgument="Image1.jpg" 
            OnClick="DownloadPicture" Width="100" Height="75" ImageUrl="~/Images/Image1.jpg" />
        <asp:ImageButton runat="server" ID="btnPic2" Text="Pic 2" CommandArgument="Image2.jpg" 
            OnClick="DownloadPicture" Width="100" Height="75" ImageUrl="~/Images/Image2.jpg" />
        <asp:ImageButton runat="server" ID="btnPic3" Text="Pic 3" CommandArgument="Image3.jpg" 
            OnClick="DownloadPicture" Width="100" Height="75" ImageUrl="~/Images/Image3.jpg" />
        <asp:ImageButton runat="server" ID="btnPic4" Text="Pic 4" CommandArgument="Image4.jpg" 
            OnClick="DownloadPicture" Width="100" Height="75" ImageUrl="~/Images/Image4.jpg"/>
        <asp:ImageButton runat="server" ID="btnPic5" Text="Pic 5" CommandArgument="Image5.jpg" 
            OnClick="DownloadPicture" Width="100" Height="75" ImageUrl="~/Images/Image5.jpg"/>
    </form>
</body>
</html>

Monday, November 01, 2010

How to implement a custom default button for a page

<%@ Page Language="C#" %>
<html>   
<head id="Head1" runat="server">
    <script type="text/javascript" src="http://code.jquery.com/jquery-latest.js"></script>
    <script language="javascript">
        $(document).ready(function () {
            $(".TextBox").bind("keyup", function (evt) {
                evt = (evt) ? evt : window.event
                var charCode = (evt.which) ? evt.which : evt.keyCode
                if (charCode == 13)
                    __doPostBack('<%= btnDefault.UniqueID %>', '');
                return true;
            });
            $(".TextBox").bind("keypress", function (evt) {
                evt = (evt) ? evt : window.event
                var charCode = (evt.which) ? evt.which : evt.keyCode
                if (charCode == 13)
                    return false;
                return true;
            });
        });
    </script>      
    <script runat="server">
        protected void Default(object sender, EventArgs e)
        {
            Response.Write(string.Format("Default button clicked at {0}",DateTime.Now.ToString("hh:mm:ss")));
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
        <asp:TextBox runat="server" ID="TextBox1" CssClass="TextBox" onkeypress="return false" />
        <asp:TextBox runat="server" ID="TextBox2" CssClass="TextBox" onkeypress="return false" />
        <asp:TextBox runat="server" ID="TextBox3" CssClass="TextBox" onkeypress="return false" />
        <asp:TextBox runat="server" ID="TextBox4" CssClass="TextBox" onkeypress="return false" />
        <asp:TextBox runat="server" ID="TextBox5" CssClass="TextBox" onkeypress="return false" />        
        <hr />
        <asp:Button runat="server" ID="btnDefault" Text="Default" OnClick="Default" UseSubmitBehavior="false" />
        <asp:Button runat="server" ID="Button1" Text="Other" />
        <asp:Button runat="server" ID="Button2" Text="Other" />
        <asp:Button runat="server" ID="Button3" Text="Other" />
        <asp:Button runat="server" ID="Button4" Text="Other" />
        <asp:Button runat="server" ID="Button5" Text="Other" />
    </form>
</body>
</html>

How to add select other/details textbox next to selection

How to remember the TreeView selection during postbacks

Markup:

<asp:TreeView runat="server" ID="trvItems" EnableClientScript="false" />
<asp:Button runat="server" ID="btnSave" Text="Save" />

Code:

public partial class Test : Page
{
    protected List<string> SelectedNodes
    {
        get { return (List<string>)(ViewState["TREENODECOLLECTION"] ?? (ViewState["TREENODECOLLECTION"] = new List<string>())); }
        set { ViewState["TREENODECOLLECTION"] = value; }
    }
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        this.trvItems.TreeNodeExpanded += new TreeNodeEventHandler(TreeNodeExpanded);
        this.trvItems.TreeNodeCollapsed += new TreeNodeEventHandler(TreeNodeCollapsed);
        this.trvItems.SelectedNodeChanged += new EventHandler(SelectedNodeChanged);
        if (!this.IsPostBack)
        {
            this.InitalizeTreeView();
            this.trvItems.DataBind();
            this.trvItems.CollapseAll();
            this.SelectedNodes = new List<string>();
        }
        else
            this.SetExapandNodes(this.trvItems.Nodes);
            
    }
    protected void InitalizeTreeView()
    {
 
    }
    protected void SelectedNodeChanged(object sender, EventArgs e)
    {
            
    }
    protected void TreeNodeCollapsed(object sender, TreeNodeEventArgs e)
    {
        this.SelectedNodes.Remove(e.Node.Value);
        this.SetExapandNodes(this.trvItems.Nodes);
    }
    protected void TreeNodeExpanded(object sender, TreeNodeEventArgs e)
    {
        this.SelectedNodes.Add(e.Node.Value);
        this.SetExapandNodes(this.trvItems.Nodes);
    }
    protected void SetExapandNodes(TreeNodeCollection nodes)
    {
        foreach(TreeNode n in nodes)
        {
            if(this.SelectedNodes.Exists(x=>x.Equals(n.Value)))
                n.Expand();
            if(n.ChildNodes.Count>0)
                this.SetExapandNodes(n.ChildNodes);
        }
    }
}

Thursday, October 28, 2010

How to change a theme dynamically

We need to assign a theme in the page preInit event to legimately change the theme dynamically.

protected override void OnInit(EventArgs e)
{
    this.Theme = "Blue";
    base.OnInit(e);
}

However there are couple of challanges if you let users to chose the theme. First one is by the pre-init phase, there are not values loaded for page controls has LoadViewState has not yet been executed.
Solution 1: You can use Request.Form[...] collection.

protected override void OnInit(EventArgs e)
{
    string theme = this.Request.Form[ddlTheme.UniqueID];
    if (!string.IsNullOrEmpty(theme))
        this.Theme = theme;
    else
        this.Theme = "Default";
    base.OnInit(e);
}

Solution 2: You can use a Session variable but we have to re-execute the page to see the session variable.

protected override void OnInit(EventArgs e)
{
    string theme = Session["theme"] as string;
    if (!string.IsNullOrEmpty(theme))
        this.Theme = theme;
    else
        this.Theme = "Default";
    base.OnInit(e);
}
protected void ddlTheme_SelectedIndexChanged(object sender, EventArgs e)
{
    Session["Theme"] = this.ddlTheme.SelectedValue;
    Server.Transfer("Page.aspx");
}

First request takes long time in a Asp.net web application

Application Pool recycle time interval.
When you deploy an Asp.net web application to IIS, as you already know each application get assigned to an Application Pool. Each application pool has a recycle interval.
InetMgr-> Application Pools -> [your application pool ] -> Advanced Settings

When the application pool execution time exceeds its configured recycle time interval application pools get recycled. When a application pool get recycled all the temporary classes which represents aspx pages need to be recreated and also all the application need re-initialize. This process may cause your uses experience long time delays for the first request to the server.
Application Pool ideal timeout.
Application Pool has ideal timeout, which means if there are no requests to the application pool for a time greater than ideal timeout IIS shutdown the Application Pool to free up resources. Zero means no timeout. So if you experience delays due to ideal timeout, you can disable ideal timeout by setting value to zero. But most of the shared hosts have this value configured to maximize the efficiency of resource utilization.
netMgr-> Application Pools -> [your application pool ] -> Advanced Settings

With asp.net 4.0
When you redeploy the site, it is inevitable for the first request it takes time as application need to re-initialize. Fortunately in Asp.net 4.0 there is a option to wake up an application immediately after you deploy the application.

<applicationpools>
  <add name="MyApplicationPool" startMode="AlwaysRunning" />
</applicationpools>

Please see this section for more information.

Thursday, October 21, 2010

Useful regular expressions

Match style tag in VS: style=(("(([:b]*[^"]*[\n]*[:b]*)*)")|('(([:b]*[^']*[\n]*[:b]*)*)'))